In recent years, ultraviolet LEDs (light emitting diodes) which emit light in an ultraviolet region, particularly having a wavelength of less than 365 nm, have attracted attention as LEDs that can be favorably used in the fields of sterilization, water purification, medical treatment, illumination, high-density optical recording, and the like.
Some of such ultraviolet LEDs are known to have a device structure formed using an AlGaN-based thin film, which is a III nitride semiconductor, as a device material. Specifically, the LEDs are III nitride semiconductor light emitting devices each having a III nitride semiconductor laminate including a light emitting layer, and a p-type semiconductor layer and an n-type semiconductor layer which are formed with the light emitting layer therebetween; a p-type electrode on the p-type semiconductor layer side; and an n-type electrode on the n-type semiconductor layer side.
In a known technique for enhancing the light emission efficiency of the light emitting device, a reflective electrode layer is provided between a semiconductor layer and an electrode that are opposite to the light extraction side of the light emitting device (for example, between the p-type semiconductor layer and the p-side electrode when the n-type electrode side is the light extraction side)(see JP 2007-158131 A and JP 2007-027540 A (PTLs 1 and 2)). The reflective electrode layer reflects part of light produced in the light emitting layer, which is directed toward the p-side electrode, thus increasing the amount of light emitted out from the light extraction side. For example, PTL 1 discloses a III nitride semiconductor light emitting device having a reflectance enhanced by forming a rhodium (Rh) layer or the like as a high reflectance electrode layer on the p-type semiconductor layer.